We’ve often heard a minister ask, “Mary MacTavish, do you take John MacDuff to be your lawful husband, to love and cherish, till death do you part?” But in 2008, hasn’t life become more complicated for such a lifetime vow?

We’ve often heard a minister ask, “Mary MacTavish, do you take John MacDuff to be your lawful husband, to love and cherish, till death do you part?”

But in 2008, hasn’t life become more complicated for such a lifetime vow? Shouldn’t Mary ask John, “Do you toss your dirty socks on the floor?” Or, “What is your risk of obesity?”

She might demand “Before we go roaming in the gloaming, send me a copy of your sperm count and what you wear underneath your kilt.”

A recent report from the University of Aberdeen, Scotland, should make every prospective bride who wants to be a mother, take a second look at her husband-to-be before she says, “I do.”

Scottish researchers repeat what we already know, that obesity often leads to heart disease, diabetes, hypertension and a variety of other ailments. But, in the highlands and lowlands of Scotland, extra pounds also lead to a low sperm count, now associated with low fertility.

Dr. Ghlyath Shayeb and her colleagues analyzed the sperm of more than 5,000 Scots and divided them into several groups according to their body mass. Men with the best body mass had the highest level of normal sperm compared to those who were overweight or outright obese.

The study showed that males who were heavier had a 60 percent chance of producing less volume of semen and a 40 percent chance of sperm abnormalities.

But how did the skinny Scots fare? Shayeb adds that underweight Scottish males with a low body mass were also likely to suffer from the same troubles as overweight males. Not too much and not too little fat is obviously the best formula for more “tiger” in a man’s sperm tank.

Shayeb’s remarks carried a more ominous warning. She claimed it was hard to find enough thin males in Scotland for the study. And since obese females are also less fertile, there may be fewer and fewer little Scots strolling over the highlands wearing kilts in the future. Extra pounds are one way to slow growth of the world’s population. But obviously one of the worst ways to do it.

Professor Neil McClure of Queen’s University, Belfast, says, “Male fitness and health are clearly linked to man’s fertility.” In other words, the fitter the man, the fitter the sperm.

But why does weight affect the production of adequate numbers of healthy sperm? Researchers believe that too many pounds, or too few pounds, may have an adverse effect on the metabolism of sex hormones. And sex hormones are needed for the production of good highland sperm.

The epidemic of diabetes is also causing havoc with Scottish sperm. Researchers at Belfast University report that males who were not overweight, but suffering from diabetes, had twice the rate of DNA damage in sperm as males without this disease. Excess sugar in the blood apparently causes more than obesity, heart attack and sore backs.

Overweight males also have more estrogen. Their fat converts the male hormone androgen into the female hormone estrogen. This is not the best mixture for the  production of sperm.

Dr. Jorge Chavarro, of the Harvard Medical School, adds another bad combination. His study shows that overweight males who eat soy-based foods have lower sperm counts. The difference was quite striking. Normal sperm counts are between 80 million to 120 million sperm per milliliter. Males eating soy had sperm counts of only 41 million sperm per milliliter.

We know that the best sperm are produced at a temperature slightly below normal body temperature. So an abundance of fat around the testicles could result in increased temperature and the risk of poor sperm.

Tight fitting jockey underwear also increases the temperature. Loose fitting boxer shorts, or no shorts, are preferable.

Dr. W. Gifford-Jones is actually Dr. Ken Walker, a practicing physician in Toronto who writes many columns at his Bristol Harbour, N.Y. residence. See the Web site www.mydoctor.ca/gifford-jones.